Leishmania species‐dependent functional duality of toll‐like receptor 2

Abstract

Toll-like receptors (TLRs) are a subset of pattern recognition receptors (PRR) in innate immunity and act as a connecting link between innate and adaptive immune systems. During Leishmania infection, the activation of TLRs influences the pathogen-specific immune responses, which may play a decisive role in determining the outcome of infection, toward elimination or survival of the pathogen. Antigen-presenting cells (APCs) of the innate immune system such as macrophages, dendritic cells (DCs), neutrophils, natural killer (NK) cells, and NKT cells express TLR2, which plays a crucial role in the parasite recognition and elicitation of immune responses in Leishmania infection. Depending on the infecting

Toll-Like Receptors 2, 4, and 7, Interferon-Gamma, Interleukin 10, and Programmed Death Ligand 1 Transcripts in Leishmanin Skin Test-Positive Reactions of Ibizan Hound Dogs

“…Therefore, the immune profile detected in LST-positive reactions in Ibizan hound dogs agree with a competent immune response in these dogs. The protective role of TLR2 in several Leishmania species such as L. infantum is described elsewhere [7] and is in agreement with the present findings as well as the TLR4-related anti-L. infantum effects [28].…”

“…Moreover, parasite DNA in LST-positive reactions was higher than in paired normal-looking skin of Ibizan hound dogs and it was assumed that LST-positive reactions presented more prominent microscopic inflammatory lesions than paired normal-looking skin as described for normal-looking skin of mildly affected dogs [19,21]. TLRs are the first to recognize Leishmania through various Leishmania-associated molecular reaction patterns leading to chemokine and cytokine expression and recruitment of inflammatory cells to the site of infection as observed in the present study [7]. In addition, these TLRs act as a connecting link between innate and adaptive immune responses [7].…”

“…TLRs are the first to recognize Leishmania through various Leishmania-associated molecular reaction patterns leading to chemokine and cytokine expression and recruitment of inflammatory cells to the site of infection as observed in the present study [7]. In addition, these TLRs act as a connecting link between innate and adaptive immune responses [7].…”

“…Effective T helper 1 (Th1) cellular immunity, with the activation of macrophages by interferon gamma (IFN-γ) and tumour necrosis factor alpha (TNF-α) is associated with the elimination of intracellular amastigotes and the control of disease progression [1,3]. Although, much of the work in CanL has focused on adaptive immune response, there is a great interest in the involvement of tolllike receptors (TLRs) in the innate immune response against Leishmania infection and how their expression could modulate adaptive immune response [4][5][6][7]. In fact, ligation of TLR during the early stages of infection by pathogen-associated motifs provides critical costimulatory signals for the initiation of adaptive immune responses [8].…”

“…In fact, ligation of TLR during the early stages of infection by pathogen-associated motifs provides critical costimulatory signals for the initiation of adaptive immune responses [8]. Although numerous studies have demonstrated that engagement of individual TLR, mainly on dendritic cells, can influence CD4 + T cell priming and effector differentiation by skewing the Th1-Th2 balance, the role of different TLRs on adaptive immune response in Leishmania infection remains an unresolved issue [7]. So far, TLR2 is one of the TLRs more frequently associated with the pathogenesis of cutaneous lesions in CanL [9,10].…”